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    SubjectRe: [PATCH v3 4/6] acerhdf: Use bang-bang thermal governor
    Date
    Hi Javi,

    Javi Merino writes:

    > Hi Peter,
    >
    > On Sat, May 03, 2014 at 06:59:24PM +0100, Peter Feuerer wrote:
    >> acerhdf has been doing an on-off fan control using hysteresis by
    >> post-manipulating the outcome of thermal subsystem trip point handling.
    >> This patch enables acerhdf to use the bang-bang governor, which is
    >> intended for on-off controlled fans.
    >>
    >> Cc: Andrew Morton <akpm@linux-foundation.org>
    >> CC: Zhang Rui <rui.zhang@intel.com>
    >> Cc: Andreas Mohr <andi@lisas.de>
    >> Cc: Borislav Petkov <bp@suse.de>
    >> Cc: Javi Merino <javi.merino@arm.com>
    >> Signed-off-by: Peter Feuerer <peter@piie.net>
    >> ---
    >> drivers/platform/x86/Kconfig | 2 +-
    >> drivers/platform/x86/acerhdf.c | 34 +++++++++++++++++++++++++++++-----
    >> 2 files changed, 30 insertions(+), 6 deletions(-)
    >>
    >> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
    >> index 27df2c5..0c15d89 100644
    >> --- a/drivers/platform/x86/Kconfig
    >> +++ b/drivers/platform/x86/Kconfig
    >> @@ -38,7 +38,7 @@ config ACER_WMI
    >>
    >> config ACERHDF
    >> tristate "Acer Aspire One temperature and fan driver"
    >> - depends on THERMAL && ACPI
    >> + depends on ACPI && THERMAL_GOV_BANG_BANG
    >> ---help---
    >> This is a driver for Acer Aspire One netbooks. It allows to access
    >> the temperature sensor and to control the fan.
    >> diff --git a/drivers/platform/x86/acerhdf.c b/drivers/platform/x86/acerhdf.c
    >> index 176edbd..afaa849 100644
    >> --- a/drivers/platform/x86/acerhdf.c
    >> +++ b/drivers/platform/x86/acerhdf.c
    >> @@ -50,7 +50,7 @@
    >> */
    >> #undef START_IN_KERNEL_MODE
    >>
    >> -#define DRV_VER "0.5.30"
    >> +#define DRV_VER "0.5.31"
    >>
    >> /*
    >> * According to the Atom N270 datasheet,
    >> @@ -259,6 +259,14 @@ static const struct bios_settings_t bios_tbl[] = {
    >>
    >> static const struct bios_settings_t *bios_cfg __read_mostly;
    >>
    >> +/*
    >> + * this struct is used to instruct thermal layer to use bang_bang instead of
    >> + * default governor for acerhdf
    >> + */
    >> +static struct thermal_zone_params acerhdf_zone_params = {
    >> + .governor_name = "bang_bang",
    >> +};
    >> +
    >> static int acerhdf_get_temp(int *temp)
    >> {
    >> u8 read_temp;
    >> @@ -440,6 +448,15 @@ static int acerhdf_get_trip_type(struct thermal_zone_device *thermal, int trip,
    >> return 0;
    >> }
    >>
    >> +static int acerhdf_get_trip_hyst(struct thermal_zone_device *thermal, int trip,
    >> + unsigned long *temp)
    >> +{
    >> + if (trip == 0)
    >> + *temp = fanon - fanoff;
    >> +
    >> + return 0;
    >> +}
    >> +
    >
    > I think you should only return 0 if you've updated the temperature.
    > Otherwise you're telling the calling function that everything went all
    > right but you may be leaving garbage in *temp. What about
    >
    > if (trip != 0)
    > return -EINVAL;
    >
    > *temp = fanon - fanoff;
    > return 0;

    Yes, sounds good. What about trip == 1? This is a valid trip point for
    acerhdf (critical) and one could argue, that it has a valid hysteresis of
    0. - Thus EINVAL would be wrong here.

    thanks and kind regards,
    --peter;


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